I came up with this 10 Cob setup a while ago. I finally decided to build it. I should warn you, it's a little odd.
So far, I'm only to 10 Flags with it, but almost anything can make it that far. Those Tall-nuts I forgot to dig up, and those normal Sunflowers are not normally there. The basis behind this strategy is not mine, it's from someone on http://forums.steampowered.com/forums/showthread.php?t=892350 (I can't find the post at the moment). When those Sunflowers are removed, this SHOULD be immune to Dolphin Riders. It's also "nearly" immune to those annoying Ambush Zombies. Catapult Zombies can be a problem, but proper Cob timing should eliminate them before they launch any basketballs. Pole Vaulters are gonna be a problem, I think. Those Cob Cannons in the back are immune to Diggers, due to the Gloom placement. Bungees can be eliminated with an Ice-shroom to freeze them once they land, or, if I'm feeling lucky, tons of Cobs. Balloons shouldn't be a problem, but I plan to bring Blover just in case.
I dunno. What do you think, guys?